A three cone rotary rock bit consists of a main bit body adapted to be connected to a rotary drill string. The bit includes three individual rotatable cone cutters mounted on three individual bearing pins extending from the main bit body. Bearing systems are provided between the cone cutters and the bearing pins to promote rotation of the cutters and means are provided on the outer surface of the cone cutters for disintegrating the earth formations as the bit and the cutters rotate. A supply of undeteriorated lubricant must be maintained proximate the bearing systems throughout the lifetime of the bit. By circulating the lubricant from a reservoir to the bearings and back to the reservoir, the life of the lubricant will be increased and a larger volume of lubricant will be exposed to the bearing surfaces.
A three cone rotary rock bit must operate under very severe conditions, and the size and geometry of the bit is restricted by the operating characteristics. At the same time, the economics of petroleum production demand a longer lifetime and improved performance from the bit. In attempting to provide an improved bit, new and improved materials have been developed for the cutting structure of the cone cutters. They have provided a longer useful lifetime for the cone cutters. This has resulted in the bearing systems of the bit being often the first to fail during the drilling operation. Consequently, a need exists for new and improved lubrication systems and bearing systems to extend the useful lifetime of the bit and to allow development of other elements that interact with the lubrication and bearing systems. In attempting to provide a new lubrication system, great care must be taken that the overall capacity of the bearing systems is not reduced.